[Solved] Flexboss, gridboss, and generator woes.

[Rezin777]

I am relatively new to everything solar. Our house is currently off-grid. I've been searching for a few weeks now for resolutions to some of the issues I'm having, but it's hard to come by specific answers to specific questions so I figured I would give in and start a thread.

Here is my setup, so far:

48 x 100w Renogy panels.
1 EG4 Flexboss21 + 1 EG4 Gridboss
6 48v 100ah Eco-worthy rack batteries in an Eco-worthy rack.
Cummins Connect 20000 generator - Model RS20AE
Everything was installed by me except the propane -> generator connections.

The solar stuff was easy enough and works fairly well. I've got my eye on some TOPCon panels once I find someone to build a permanent home for them. Until that happens, I'm relying on the generator far too much (it rains daily for whatever reason) and that's where the issues arise.

For starters, the Cummins generator wants a Cummins ATS. I did not realize this when I purchased it or I would have gone another route. The Cummins also needs AC power to keep the battery charged and the system ready. I will worry about that later though. What I need is a way to use the dry contacts from the Gridboss to start and stop the generator. Current work around is to walk out to the unit and start it manually using the local controls.

A few minutes after the generator starts, it will take over the loads from the battery/solar. About 10 minutes after taking over the loads, it will start charging the batteries. I have no idea why it takes this long. Occasionally, and randomly, the generator suddenly stops supplying any power to the system. Battery charging stops, and the loads go back to the solar/batteries. The generator is still running, at idle. After a short period it will seem to "recover" and again take over the loads, and then a while later start charging the batteries. Sometimes, without dropping the charge/loads, it will charge the batteries to the "Charge End SOC(%)" setting that I've chosen at which point it stops charging and continues to handle the loads.

I have no idea if any of that behavior would change if I had the remote stop/start functioning properly. I have my doubts. I've changed settings, such as "Batt Charge Current Limit(Adc)", so the generator was only working at half it's rated power. That doesn't help. I've had it working close to it's rating with some extra loads (dryer), and it continued to charge the batteries until the SOC cut off.

I've gotten the event "W015: GEN voltage and frequency abnormality" a few times, however it does not coincide with the generator dropping the charging/loads. In fact just before I started writing this post, the generator was running and dropped the charging/loads and I have no alerts from today at all.

When the generator takes over the loads, everything is smooth, however when it starts (or stops) charging the batteries the power to the house "flickers". It's very strange though. I have a Bluetti UPS (AC200L) on my PC, which has worked flawlessly during grid outages (back when we were on the grid), however during one of these power fluctuations, my computer monitor and PC will restart anyway. Ceiling lights, without a UPS of course, seem unaffected. I've toggled "Seamless EPS switching" on and off to no avail.

I was running the shipped firmware for most of this time. However I finally gave in and toggled the "* Remote tech support" to accepted and updated the firmware for the Flexboss. I had already updated the Gridboss with the phone app. I did not use the phone app for the Flexboss because it was not listed in the drop down menu, although as I understand it, the 18KPV firmware is also for the Flexboss21. Updating did not change any of this behavior.

So I guess I'll ask a few questions now.

Is there a semi-easy way to control the Cummins RS20AE with the Gridboss? I am not opposed to wiring up a relay, but I would need detailed instructions. Buying a device to place between the two and simplify my life would be fantastic.

Why is the house power flickering when the Generator starts/stops charging the batteries? I purchased the Gridboss specifically because it seemed to be well suited to function with a generator. I'd actually prefer the generator only charge batteries, instead of taking over the loads. I don't believe that is an option in the settings available to me.

Unrelated to the generator. It seems to me that the cable provided with the Eco-worthy batteries are undersized for an entire rack. I've got 4/0 from the master battery to my busbar, yet the remaining 5 batteries are supposed to be charged through the 2 awg(?) they provide? Doesn't make any sense to me. I've already purchased 2/0 to replace the 2 awg between the batteries. A busbar in the rack would make the most sense. I've also considered connecting not only the master battery (top rack space) to my busbar, but the last slave battery (bottom rack space) as well with the previously mentioned 4/0. Is there any reason not to do such a thing? The last slave battery has two open terminals there for the taking.

I plan to rebuild this entire system in the near future with different hardware. The EG4 stuff was quick and easy, but I don't know that I'm ready to rely on it for the coming winter months. The instructions are lacking, the monitoring software is buggy and weird, and I just don't know if any of it is living up to my expectations.

The Eco-worthy batteries however, have been fantastic (besides what I consider undersized cables but maybe I'm doing it wrong)!

Sorry for the long post, I just don't know how to describe it with less words. I'm happy to answer any questions about settings or whatever.

 

[SunDave]

A few minutes after the generator starts, it will take over the loads from the battery/solar. About 10 minutes after taking over the loads, it will start charging the batteries. I have no idea why it takes this long. Occasionally, and randomly, the generator suddenly stops supplying any power to the system. Battery charging stops, and the loads go back to the solar/batteries. The generator is still running, at idle. After a short period it will seem to "recover" and again take over the loads, and then a while later start charging the batteries. Sometimes, without dropping the charge/loads, it will charge the batteries to the "Charge End SOC(%)" setting that I've chosen at which point it stops charging and continues to handle the loads.

Hi. I'll take a crack at a couple of these. It could be that the generator is not providing clean enough power, but it could also be that you are exceeding what the generator can output. For example if you run 12,000 watts charging, the water heater is running, and you kick on a dryer, that will exceed the generator's rating. The inverter won't just switch to battery and then back seamlessly. When you are charging from the generator, you need to charge at a low enough rate to power the loads, and the charge. Or limit your household loads while charging. Keep in mind things like a water heater that can cycle without you doing anything.

If you are exceeding the generator's capacity that explains the recovery time. What is happening is that your whole system is switching back to solar and battery like you describe. Then after a wait period, charging is attempted again.

Unrelated to the generator. It seems to me that the cable provided with the Eco-worthy batteries are undersized for an entire rack. I've got 4/0 from the master battery to my busbar, yet the remaining 5 batteries are supposed to be charged through the 2 awg(?) they provide? Doesn't make any sense to me. I've already purchased 2/0 to replace the 2 awg between the batteries. A busbar in the rack would make the most sense. I've also considered connecting not only the master battery (top rack space) to my busbar, but the last slave battery (bottom rack space) as well with the previously mentioned 4/0. Is there any reason not to do such a thing? The last slave battery has two open terminals there for the taking.

Normally busbars are used as a hub. Meaning each battery has it's own connection to the busbar and then from the busbar to the flexboss the 4/0 would be used. If the batteries are all daisy chained now, then your ability to charge at high rates without making the wires very hot will be limited. Pictures of how the batteries are wired would really help forum members to help you.

I can't help with the generator start question. I have only seen two wire start compatible models.

 

[Rezin777]

Hi. I'll take a crack at a couple of these. It could be that the generator is not providing clean enough power, but it could also be that you are exceeding what the generator can output. For example if you run 12,000 watts charging, the water heater is running, and you kick on a dryer, that will exceed the generator's rating. The inverter won't just switch to battery and then back seamlessly. When you are charging from the generator, you need to charge at a low enough rate to power the loads, and the charge. Or limit your household loads while charging. Keep in mind things like a water heater that can cycle without you doing anything.

Thank you for taking the time!

The generator is rated at 20000w and less than 5% THD. I'm very aware of the loads of the house at all times, since I've been troubleshooting this for a while now. The water heater is a heat pump type set to heat pump only. There is no sudden large draw from the house unless I cause it on purpose.

I typically start the generator when there is minimal load, 600w total or so. The generator will first take over the load, and later start charging the batteries. As soon as the battery charging starts, the power will flicker. When the battery charging stops, the power will flicker. This behavior always happens. I should point out that there is no flicker when the Gridboss switches the loads from battery to generator.

The generator will drop charging/loads seemingly randomly. I've had it charging the batteries at 250 amps with the dryer running at the same time (I was pushing it here on purpose) and it did not drop the charging/loads. It was supplying around 17000w at the time. It ran fine until the dryer stopped and the batteries were charged to the SoC setting.

Yesterday it was charging at 200 amps, the house was pulling about 1000w, the total usage including battery charging was about 11000w and it suddenly dropped charging/loads, ran at idle for a time, then picked up the loads and a short time later started charging the batteries again. It then charged until it reached the SoC setting. It was a very steady 11000w during the entire time. There is a very audible click, I assume a relay, from the Gridboss or Flexboss when this happens.

Perhaps I'm expecting too much from the Gridboss here? From the manual:

For optimal performance, it is highly recommended that a generator have less than 12% Total Harmonic Distortion (THD). To achieve a lower THD value, the generator should be sized by at least 1.5x the total output of all inverters. This will allow for powering loads and charging batteries.

I can see 17000w being too much, however it did not fail during that "test". It did fail at 11000w, recovered and then completed the charge. I don't know how to make sense of that.

Should I really expect the house to flicker when battery charging kicks in? I purchased the Gridboss hoping it would handle the generator. How about I hook the generator into the grid input instead? Shouldn't the Gridboss be able to swap between grid and battery seamlessly? If not, my expectations are apparently way off here.

Normally busbars are used as a hub. Meaning each battery has it's own connection to the busbar and then from the busbar to the flexboss the 4/0 would be used. If the batteries are all daisy chained now, then your ability to charge at high rates without making the wires very hot will be limited. Pictures of how the batteries are wired would really help forum members to help you.

I have 6 batteries daisy chained with the cables supplied from the manufacturer (3 awg, my mistake when I said 2 earlier). The master battery is then connected to the busbar with 4/0. The busbar is for future expansion / chargeverter, etc. The busbar is then connected to a 200a breaker/disconnect with 4/0 and after the breaker its 4/0 to the Flexboss.

The first wire in the daisy chain (from master to first slave) tends to get warm (not hot) during generator charging. This is why I've purchased 2/0 for the daisy chaining (not installed yet). A busbar built into the cabinet would be optimal, I think. I would not want to connect each individual battery to the external busbar, as part of the benefits of the rack system is the cleanliness of the install.

I was wondering if there is any harm in adding a second 4/0 from the server rack batteries to the busbar, from the bottom battery (final slave opposite the top master). I don't see any reason why this would cause any issue, other than a slightly less clean install. But I ask because I am still new at this. Having two paths to the busbar at opposite ends of the rack should ease the demands put on the daisy chained connections?

Here is a pic, with the proposed new connections in yellow and green for visibility.

 

[SunDave]

Thank you for taking the time!

No problem. Lots of us have been through similar initial fights. I could throw out some random ideas that may help first, then see if I can help with specifics. Take it or leave it. Not telling you how to approach this, just throwing out options.

• You may want to approach the items one at a time on the forum, with specific post titles. Many of the very helpful people on the forum don't respond to the very large posts with multiple items.
• You may want to prioritize adding solar. You have more battery than solar. I have the same 30kWh of battery. I started with a 2kW watt setup at home, and eventually went to 13.76kW. That move made even more of a difference than it sounds like because I was burning approx 2000 watts a day just in idle draw. When I went bigger, even if I would have doubled it, I would have gotten more than double the usable power in return. We are on our best days of the year now in the northern hemisphere, so it only gets worse from here. The generator problems become less with solar. It becomes a true occasional use device. You could reach out for budget friendly ways to do this on a post as well. Include specifics about your mounting options of course.

I can see 17000w being too much, however it did not fail during that "test". It did fail at 11000w, recovered and then completed the charge. I don't know how to make sense of that.

Should I really expect the house to flicker when battery charging kicks in? I purchased the Gridboss hoping it would handle the generator. How about I hook the generator into the grid input instead? Shouldn't the Gridboss be able to swap between grid and battery seamlessly? If not, my expectations are apparently way off here.

I see that you have looked into it quite a bit. It is possible that you could get a good or more detailed readout of error codes on the web interface, and then troubleshoot this one with EG4, or where you purchased it. Again a separate post is an option. Another option is troubleshooting 101. If you have another generator, even a smaller one you can borrow that could be tested, that could tell you if it is a problem with the generator somehow.

I did think of one thing that points to your troubles being potentially related. If you have battery communications you could confirm this. It is possible that your batteries being wired like they are leads to your generator shutting off. One of your batteries may be getting to max voltage way before the others. Battery communications, or even possibly errors on the inverter webpage could yield more info.

I have 6 batteries daisy chained with the cables supplied from the manufacturer (3 awg, my mistake when I said 2 earlier). The master battery is then connected to the busbar with 4/0. The busbar is for future expansion / chargeverter, etc. The busbar is then connected to a 200a breaker/disconnect with 4/0 and after the breaker its 4/0 to the Flexboss.

Thanks for the picture, that really helps. If you think about how power flows, that cable between the first battery and the next is taking on all the current for the 5 below it, meaning that it is over a reasonable amperage rating with that wiring config. I would suggest lowering your max charge to around 5,000 watts . That is the power that one battery could take on a max charge because that is what the cable is spec'd for. If you add a cable to the other side you could theoretically double that but you would still see charge imbalance issues due to the cable length mismatch. And only doubling it is not really what you want if you are trying to fix it up.

In your setup, to better balance the charge without spending a lot, it would help to have the positive cable on the top, and the negative on the bottom. Be careful to properly shut down the system when swapping cables around. We don't want big sparks.

The best way to wire it would be each battery to the busbar. I have a similar battery and have two batteries wired together, then a positive from top, and a negative to the bottom one, that runs to a busbar. So they are essentially wired in pairs, those pairs can handle 100 amps each, so with 3 pairs I can easily get a full power charge. So there is the ideal way, in the middle ways, and even simple ways like making your connection diagonal so the batteries charge more evenly. You have several choices for improving the battery setup.

I hope this helped. You will get there.

 

[Kant_Hack_It]

I agree with SunDave here, with both of your leads going from the rack to your inverter on one battery, you could be hitting the soc on that battery well before the others. I'd personally drop either one off the main leads to the bottom battery and that'll charge batteries more evenly.

 

[SunDave]

This is why I've purchased 2/0 for the daisy chaining (not installed yet).

I see now you have better cables too (the trouble with long posts right ). That along with what Kant_Hack_It said about making that main connection diagonal will solve your battery cables, and could solve the generator charging issue.

 

[Rezin777]

I realize long form is dying, but growing up with forums instead of social media, that's how I tend to communicate. I try to avoid starting threads at all, and generally feel uncomfortable starting a new thread for every issue. I would feel like I'm "spamming" the forum and taking up space where other people might ask for help.

I do plan to add a lot more solar. I'm installing all of this myself however, and just don't have the time to tackle a ground mount at the moment. This system had to be installed in a bit of a rush and the Renogy panels are what I happened to have on hand. I hope to start ordering more panels in the near future. Specifically I'm considering TOPHiKu6 panels. I don't know of any reputable solar installers that would do partial work (just the ground mount) in northern PA. Typically when I pay for work I'm disappointed, so I end up doing everything myself.

I don't think I will stick with the EG4 products in the long run and have already started purchasing Victron gear for the future. Having everything in one unit is nice for installation, but I worry about reliability. I firmly believe that if you have one, you have none.

I've been working on the 2/0 daisy chain cables today. When I finish I will shut the system down, replace the 3 awg cables, and move the negative lead to the bottom battery.

I guess I will see if any of that fixes any issues before looking further. Perhaps if some of the issues do get resolved I will start a more dedicated thread about my biggest issue, the generator remote start.

Thanks guys.

 

[Rezin777]

I rewired the battery rack with 2/0 cables and moved the location of the negative lead. After doing this I started the generator to test things, careful to pay attention to all the details I could.

I must have been mistaken about the power fluctuations I noticed before. They occur when the Gridboss switches loads to the generator and then back to the battery. The lights in the house do not go out, but my UPS reacts. This time, however, the fluctuations seemed to be less intense. Perhaps it's placebo effect. There was no fluctuation when the Gridboss starts charging the battery.

The Gridboss switches loads to the generator after 1 minute. This is a setting in the monitoring software. The batteries start charging 5 minutes after that. I do not see any way to change that, however I wish it could happen sooner.

Charging was not interrupted this time. I am hoping the interruptions were due to the previous battery wiring. I will keep monitoring this. Charging seemed faster. Again, it could be placebo effect, or perhaps the improved wiring changed things.

I had set the generator to stop charging at 90% SoC prior to starting the generator. After the generator started charging, I changed that setting to 100% since things were going so smoothly. However, charging stopped at 90%, and loads were also dropped at this point. After a minute loads switched to the generator again. Seems a little odd. I will run the generator again tomorrow to check if it charges to 100%.

The new daisy chain cables still got warm to the touch on the batteries closest to the main cables. I wonder if even larger cables would be worthwhile. I am not opposed to just putting 4/0 everywhere.

Thanks again for the suggestions. I'm hoping for enough sun later in the week to get a full charge and balance the batteries now that the wiring is improved. I still think Eco-worthy should make a bus bar for their rack. I am under the impression that EG4's rack does include one, although I may have read it was undersized.

 

[SunDave]

Great. Sounds like you have some progress. There is a limit on how much larger cables as interconnects would help. The limit being the connection within the battery itself. It's possible that Eco-Worthy has some information about how many batteries can be daisy chained and retain full capabilities.

You can see just from the lights that your bottom batteries seem to have less charge yet, but that may change now after some charge cycles.

 

[kc130up]

I have an FB21 + GB and will connect my generator to it for the first time tonight. My genny is only 9kW which is enough for the entire house 90% of the time. Only the HWH and Dryer pushes consumption over 7kW.

I'll let you know how seamless the transition between battery / generator go when i test it!

 

[Rezin777]

Thanks! Any additional information is always helpful.

I will elaborate on the transition a bit. The lights do not go out but may or may not flicker. I have several things on UPS (several Bluetti and one APC). When the system switches over to generator or back, the UPS all react in some way, and my computer actually shuts off sometimes. It's weird because it's on a UPS which functioned well during actual power outages back when we were on the grid.

Since I started this thread I was able to get the generator to work with the 2 wire dry contacts of the Gridboss. I'm very pleased about this, however there is some strange behavior. Also, charging still cuts out randomly for unknown reasons. No reporting in the Monitor Software to let me know what's happening.

For starters, this Monitor setting.



Choosing Enable here starts the generator immediately. The generator does not shut off after reaching the set "remote auto turn off time". I have to choose Disable here to shut it off. I would have assumed this simply enables the generator to turn on with the "Start Generator" button on the main page.



The SoC generator charge setting works as expected. When the SoC drops to the percentage set, the generator will start, when the SoC reaches the percentage set, the generator will stop. Nice.

However, I'm still getting interruptions during charging. Here I had "Batt Charge Current Limit(Adc)" set to 200 A. It interrupted rather quickly, so I bumped it down to 150 A. As you can see it ran for quite a while but then interrupted again before reaching the SoC percentage set. The battery BMS did not seem to cause this interruption as it was still at its maximum "BMS Limit Charge: 600 A" and the batteries were nowhere near full (this was charging from around 30% SoC to 75% SoC.

My guess is that the Generator puts out some dirty power and the EG4 stuff disconnects it. However, this was at 11000w and 8000w on a generator rated for 20000w. The generator is new and supposed to be less than 5% THD. There was no variation in engine sound when these cut outs occurred.



Since we have some sunny days finally, I'm hoping to get the batteries balanced again and see if this fixes any issues.

 

[kc130up]

It is odd that the GB stops accepting power from the generator. If the generator occasionally provides dirty power and the GB cutting it off makes logical sense BUT, i've found many EG4 settings don't always follow logic. They work, just not the way they are written.

I have no experience in this area to help, so I am watching as you learn!

Be nice to have a friends generator to test with. Even a 1 day rental unit would provide valuable data.

 

[kc130up]

I got the generator port installed. I couldn't test the generator failover as the wife was already tapping her foot for the 35 min power was out while I worked on the generator port setup.

I did see the generator symbol on the GB show 244 vac. I didn't see a way to have the GB switch loads to the jenny without me flipping the blade disconnect.

I will have to wait a few days for another "shutdown" test

I will have to wait a few days to ask for a "shutdown" test...haha.

 

[Redpineapple]

I got the generator port installed. I couldn't test the generator failover as the wife was already tapping her foot for the 35 min power was out while I worked on the generator port setup.

I did see the generator symbol on the GB show 244 vac. I didn't see a way to have the GB switch loads to the jenny without me flipping the blade disconnect.

I will have to wait a few days for another "shutdown" test

I will have to wait a few days to ask for a "shutdown" test...haha.

View attachment 309902

Any update on this?

 

[kc130up]

I have not tried the generator again. Managing the issues from the firmware update.

I used two "unscheduled shutdown" wife-credits doing reboots for the firmware update. I need to built my solar-wife-credit account back up.

 

[Usernameinuse]

Are those credits purchasable? I am in the negative as well.

 

[Redpineapple]

I wish I knew about the new firmware settings that came out 2 weeks ago!

EG4_FAAB-2122​

2025-06-22​

• Based on FAAB-2021
• 1.Add Weekly Setting function.
• 2.Add the function of Sporadic AC charge power function, it will cause the AC charge power to fluctuate randomly between the set AC charging power and 2% rated power.
• 3.Optimize the response speed and stability in zero export mode in meter mode.
• 4.Optimize the restart logic that modify the CT/meter, battery type and brand will not be restarted.
• 5.Improve the issue of reading the RGM settings.
• 6.Improve the issue of power display on Micro-Grid mode.
• 7.Improve the issue of not stopping at the Stop Discharge Volt of forced discharge.
• 8.Improve the issue where the LCD display on the load power side lacked Smart Load power when the Micro Grid plus Smart Load mode were enabled.
• 9.Improve the issue of increased charge power when setting the Charge Last mode.
• 10.Improve the issue of abnormal load display in web page flow chart during parallel mode.
• 11.Improve the issue of getting phase lost warning when switching from on-grid and off-grid in three phase parallel mode.

I assume no one has had issues with this?

 

[RARankin]

Mine have been running just fine since I updated to 2122.

 

[Redpineapple]

I have not tried the generator again. Managing the issues from the firmware update.

I used two "unscheduled shutdown" wife-credits doing reboots for the firmware update. I need to built my solar-wife-credit account back up.

What “issues” do you have from the update?

Just curious

 

[kc130up]

Issues wasn't the best word, makes things seems more serious than they are. My only issue is something weird with the display/reporting.
Battery drain shows as solar input.

When peak shaving kicks in at 5pm, the dashboard shows the battery usage as solar power. The sun is gone and solar is almost nothing come 6pm.



According to the dashboard, I'm getting 4.5kW spikes of solar after sunset.

My max power at noon is ~3.3kW

 

[comet48]

There are other posts with GB dropping generator. Apparently the GB doesn't work well with AC input, like generators and enphase inverters. Hopefully this is addressed before the tax credits expire so I can make a purchase.